A comprehensive analysis is one of the methods of an analysis using a mass analysis. In the comprehensive analysis, all the results obtained from mass analyses for a plurality of samples are compared. In an analysis of this kind, a multivariate analysis is generally used such as a discrimination analysis, a principal component analysis, a cluster analysis, or other analysis.
For example, Non-Patent Document 1 discloses a software program for performing a principal component analysis of mass spectrum data obtained from a mass analysis. Non-Patent Document 2, Patent Document 1, and other documents disclose examples in which mass spectrum data obtained for a plurality of samples are processed by a principal component analysis and the results are presented using the charts called the “scores plot” and “loadings plot.” The scores plot presents the results of the principal component analysis in such a manner as to enable users to easily recognize the grouping of plural samples. The loadings plot provides information about which compounds (components) contribute to the grouping of those samples and to what extent.
Some of the recently developed mass spectrometers can obtain MS1 spectrum data, which are a result of an MS1 analysis, and also MS2 spectrum data, which are a result of an MS2 analysis in which an ion dissociation operation is performed (for example, refer to Non-Patent Document 3). In such a mass spectrometer, immediately after a normal mass analysis (MS1 analysis) is performed, a peak or peaks appearing on the MS1 spectrum obtained by the MS1 analysis are selected under predetermined conditions (for example, a predetermined number of peaks are selected in descending order of their peak intensity). Then, the mass-to-charge ratios of the selected peaks are set as the precursor ions, and the precursor ions are selected and dissociated. A variety of product ions generated by the dissociation are mass analyzed to obtain MS2 spectrum data. Such MSn spectrum data generally include structural information on a target component, which is useful for the identification and structural analysis of the component.
Using MSn spectrum data in a comprehensive analysis probably allows a more accurate or more detailed analysis. However, the data used in the aforementioned conventional comprehensive analysis are mostly MS1 spectrum data. Even in the case where an MSn analysis is performed, MSn spectrum data are merely used for the deduction of the composition of each component, database search, or other purposes after the comprehensive analysis using MS1 spectrum data is completed.